Identification of lung adenocarcinoma mutation status based on histologic subtype: Retrospective analysis of 269 patients

Background To evaluate differences in the clinical characteristics and molecular pathology of lung adenocarcinoma subtypes as defined by the new I nternational A ssociation for the S tudy of L ung C ancer/ A merican T horacic S ociety/ E uropean R espiratory S ociety international histological classification. Methods We retrospectively reviewed 269 patients with initial primary lung adenocarcinoma who had undergone complete resection at our department from A ugust 2013 to D ecember 2014, focusing on the new histologic subtype classification, clinical characteristics, and molecular pathology. Results All specimens were invasive adenocarcinoma, and were lepidic (13.0%), papillary (19.7%), acinar (51.7%), solid (8.6%), micropapillary (1.1%) or mucinous predominant (5.9%). Epidermal growth factor receptor ( EGFR ) mutations were detected in 132 cases (60.3%). Female patients and non‐smokers had higher EGFR mutation rates ( P = 0.022 and 0.026, respectively). The lepidic, papillary, acinar, solid, micropapillary, and mucinous predominant patterns had EGFR mutation rates of 70.6%, 64.8%, 72.5%, 33.3%, 100%, and 5.9%, respectively. The exon mutation distribution differed according to serum carcinoembryonic antigen ( CEA ) levels ( P = 0.018). v‐ K i‐ras2 K irsten rat sarcoma viral oncogene homolog ( KRAS ) mutations were detected in 20 cases (9.2%), and were frequently found in the mucinous and solid predominant subtypes. The serum CEA levels differed among the subtypes. Conclusions In C hina, there are significant differences between lung adenocarcinoma histologic subtypes. The presence of well‐differentiated components in lung adenocarcinoma indicates higher EGFR mutation rates; the presence of solid or mucinous components indicates higher KRAS mutation rates. Serum CEA levels are associated with histologic subtype and EGFR exon mutations.